1. Field of the Invention
The present invention relates to a choke coil mounted on a printed circuit board, for example, and particularly to a choke coil suitable for high-frequency uses.
2. Description of the Related Art
Choke coils are generally mounted in large numbers in high-frequency printed circuit boards and the like of electronic equipment. These choke coils are used for a wide variety of purposes and are manufactured in various constructions depending on their intended use.
However, choke coils alone cannot be used in broadband circuits covering a range from low frequencies to microwave bands because the Q-value of the coil rises too high. Therefore, resistors and the like are conventionally connected to the choke coils in order to maintain a suitable Q-value.
In recent years, however, electronic equipment has become smaller and more lightweight at a rapid pace, requiring that electronic parts be mounted at a higher density on the printed circuit board. When mounting a plurality of the conventional choke coils described above on a printed circuit board, therefore, it is necessary to connect them close together in series. With this configuration, neighboring choke coils may become magnetically coupled due to leakage flux between choke coils (magnetic flux near the ends of the choke coils). This causes the resonance frequency to shift toward the low frequency end, preventing the choke coils from performing their intended function.
When choke coils are mounted on a printed circuit board to eliminate noise or the like from the power terminals of operational amplifiers connected in multiple stages, a choke coil in one stage may become magnetically coupled to a choke coil in the following stage due to the leakage flux described above. Such magnetic coupling can generate oscillations.
In view of the foregoing, it is an object of the present invention to provide a choke coil for broadband use including the microwave band that is capable of being densely mounted on a printed circuit board and that is capable of preventing oscillations generated by neighboring choke coils becoming magnetically coupled.
These objects and others will be attained by a choke coil comprising a coil having an insulated conducting wire wound in a coil shape; and a conducting ring having a centerline extending in the axial direction of the coil.
In a choke coil having this construction, the conducting ring can be disposed one on either end of the coil or only on one end of the coil Further, the ring and coil are arranged sequentially in a straight line. The distance between the coil and ring is set according to the intended use.